Defining fair trade has been one of the challenges for companies like Fair Indigo that want to go mainstream with a concept many still see as existing only in the margins. At its most basic, the term indicates that the people who create the product are paid a living wage and have decent working conditions. Some expand that definition to include having the right to unionize and access to health care. Others, including the Fair Trade Federation in Washington, D.C., limit it to apply only to workers in developing nations. Often those who support fair trade also support the use of organics and other green initiatives, concerns that are tangential to fair trade, which is all about the labor practices.

"There's this perception of fair-trade clothing being made out of hemp, but that's not the case," says Patti Freeman Evans, a senior retail-industry analyst for New York-based JupiterResearch. "Bill certainly makes the business case for stylish, reasonably priced, competitive fair-trade apparel."

Concerning coffee - the unequivocal fair-trade success story - the process is simpler because coffee (like cocoa) is a commodity. Growers can be paid a fair market price for their goods, one that can be applied universally. The Specialty Coffee Association of America estimates that in 2006, 3.3 percent of coffee sales in the United States were fair trade (TransFair USA calculates this at a retail value of $730 million), thanks to support from megaplayers such as McDonald's. Two years before that, those figures were 1.7 percent and $369 million.

Clothing is more complicated because it is not a commodity. Everyone, from the cotton growers to the factory workers who hem the pant legs, needs to be paid a living wage, and the cost of the end product differs, based on a number of subjective criteria such as designer labels. So far, there hasn't been a McDonald's equivalent in fair-trade apparel. If a company like the Gap decided to convert all its factories to fair trade, the category of fair-trade apparel would certainly get a boost. But Evans says that at present, there are not enough fair-trade factories to handle that kind of volume.

It's impossible to pinpoint the exact value of all fair-trade products, partly because there is no U.S. certification of fair-trade apparel. But estimates of the domestic nonagricultural fair-trade market range from $200 million to $225 million.

"I feel the U.S. is slow to start but will move at a faster pace to bring fair trade to scale," says Stacey Edgar, president of Global Girlfriend, a Colorado firm that sells fair-trade goods made by disadvantaged ­women. Edgar became aware of fair-trade issues after her mother-in-law, the former first lady of Illinois, told her about the working conditions she'd seen when traveling to developing countries.